This could easily be integrated in the driver (it would be much more
easy to do than writing a separate program) but like you say in your
disclaimer: we cannot guarantee that nothing bad happens. Therefore
I don't think it is the way to go.
However what I find more interesting is that you updated the BIOS with
one form the Intel web site. Intel claims that this issue has been
fixed with later versions of the BIOS, so that the driver can use a
specific BIOS function to teach the BIOS of the changed size.
Therefore - according to Intel - you should not need this program 
any more.


Christian Zietz writes:
 > Hi,
 > PLEASE CC any answers to [EMAIL PROTECTED] as I'm not subscribed to the list.
 > first,  my problem as summarized by David H. Dawes:
 > It appears that some 855GM-based laptops only pre-allocate 1MB of video
 > memory, and don't provide any BIOS configuration options for increasing
 > this. Although the XFree86 driver will allocate more (if the correct
 > agpgart kernel support is present), the mechanism used to inform the
 > video BIOS of the additional allocation doesn't seem to be implemented
 > on these laptops. This results in the video BIOS refusing to program
 > video modes that require more than 1MB (actually 832KB).
 > As far as I know there hasn't been any solution for this. So I spent my
 > day digging through Intel datasheets and disassembling the Video BIOS
 > and came up with a hack that works for me:
 > The Video BIOS stores the memory size it thinks it is allocated at a
 > certain location in RAM. This location is write-protected by default but
 > can me made writable by setting the appropiate chipset registers. That's
 > what I do and then I can set the memory size so XFree86 works with
 > higher resolutions and color depths.
 > Since I don't have the XFree86 sources to patch, I implemented this hack
 > in a separate program called 855patch. It takes the desired video memory
 > size in KB as argument. Note that it only tells the BIOS what memory
 > size to expect but does NOT actually allocate the memory. So you'll have
 > to set the VideoRAM option in the XF86Config Device section to at least
 > the size you used when calling 855patch (more is fine) or your system
 > will probably crash.
 > The hack works nicely on my Dell Inspiron 500m laptop (Intel Video BIOS
 > version 2945) and the mechanism I described is also implemented in
 > version 2973 I downloaded from So I suggest you try it, if
 > you have the problem described above. I'd be very glad if this snippet -
 > if it works on other systems - found it's way to XFree86 sources.
 > Disclaimer: Obviously I can't guarantee that it'll work for you. So
 > don't blame me if something bad happens.
 > Download:
 > Christian Zietz, now able to run XFree86 in 1024x768x16bpp
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